Field experiments were conducted in 1986 and 1987 to determine the efficacy of various herbicides applied in the spring or fall for redvine population reductions. Spring applications of dicamba and picloram reduced redvine populations 4 mo after application. These treatments also reduced soybean density. A sequential spring followed by fall application of dicamba reduced redvine stem counts 32 to 45% the following year. Spring or spring followed by fall applications of clopyralid and hexazinone were not effective in reducing redvine populations. A fall application of clopyralid, dicamba, Dowco 433, glyphosate, or imazapyr reduced redvine regrowth 78 to 97% the following year. Dicamba at 2.2 kg ae ha-1, 3.4 kg ae ha-1 glyphosate, and 0.28 kg ai ha-1 imazapyr increased soybean yield the following year because of reduced redvine competition and lack of herbicide injury. Redvine populations were unaffected by fall applications of fosamine, hexazinone, and picloram, or clomazone applied in the spring or in the fall followed by a sequential spring application. A sequential spring followed by fall treatment of 1.1 + 1.1 kg ha-1 dicamba or 0.14 + 0.14 kg ae ha-1 clopyralid reduced trumpetcreeper population 49 to 58% the following year.

The effects of environmental factors on germination and emergence of Campsis radicans seeds were examined in laboratory and greenhouse experiments. Campsis radicans pods produced numerous, papery, and small seeds (696 seeds/pod; 4 mg/seed). Seeds exhibited dormancy that was relieved (74% germination) after 2 wk of prechilling. Fluctuating temperatures and a 12-h photoperiod were required for maximum germination. Optimum conditions for C. radicans seed germination (74%) were 35/25 C (day/night, 12/12 h) with a 12-h photoperiod. Temperatures below 25/15 C or above 40/30 C were unfavorable for germination. Germination in constant temperatures or in continuous darkness was less than 15%. More than 59% of C. radicans seeds germinated at pH 5 to 9, but at pH 4 or 10 seed germination was totally inhibited. Germination was totally inhibited at osmotic stress higher than −0.2 MPa. Germination was 60% at 40 mM NaCl and 20% at 160 mM NaCl. Emergence was maximum (68%) for seeds that were placed on the soil surface, but no seedlings emerged from a soil depth at 4 cm. About 10% of seeds were still viable even after 20 wk of prechilling. Each pod contained about 700 seeds and each plant produced 20 to 40 pods. These results suggest that the spread potential of C. radicans by seeds would be at least 1,400 to 2,800 seeds plant−1. However, only seeds near the soil surface would be able to germinate.